This invention relates to a date indexing device for an analog (hands) watch with a rotatable date indication carrier or "date ring," which has at least one toothed rim for the purpose of its indexing, and with a driving gear between the motor of the watch and the data ring, as well as a setting member for the manual indexing of the date ring.
With conventional analog watches, whether these have a mechanical or an electric motor, it is always troublesome and time-consuming to have manually to index the date ring at the end of a month with less than 31 days since in most cases, with the aid of the watch's crown, the hands must also be adjusted. If, however, a quick-setting procedure is provided (cf. e.g. U.S. Pat. No. 3,413,800 or U.S. Pat. No. 4,291,397), with the aid of which the date ring is adjustable without the hands of the watch being moved, two problems arise. Firstly, any damage to the watch's gearing upon actuation of the quick-setting device must be prevented and, secondly, the date ring should not be able to readjust itself inadvertently if the watch is subjected to any shocks. These two problems have not so far been satisfactorily solved.
The object of the invention was, therefore, to develop a date indexing device for an analog watch, with which the date ring is indexable quickly and simply without adjusting the hands, but without there being any danger of the date ring being inadvertently readjusted when subjected to the normal shocks which occur during use of the watch. Based on a date indexing device of the type mentioned at the beginning the object is resolved according to the invention by designing the setting member as a push button which operates an indexing pawl for indexing the date ring and by the driving gear having a gear element, which is disengageable when the push button is actuated. Firstly, the date ring is indexable directly, i.e. without adjustment of the hands, and in a simple manner; secondly, the danger of the watch's gearing being damaged when a correction is made to the position of the date ring is eliminated by the disengageable gear element. Finally, as the date ring is always connected with the driving gear when the push button mentioned is in its rest position it is as good as ruled out that an incorrect positioning of the date indication carrier will result if the watch is subjected to the shocks which occur during use.
In order to be absolutely certain that actuation of said push button during the time period including midnight, during which the date ring is indexed, does not lead to the watch being damaged it is advisable to have merely one spring, which operates the quick-setting procedure, tensioned by this push button; this spring then accomplishes the indexing of the date ring; for this purpose one preferred embodiment of the date indexing procedure according to the invention is provided with a spring tensionable by the push button; the date ring is indexable by the indexing pawl during the return stroke of this spring. In the case under consideration the spring merely assists the automatic indexing of the date ring.
In order that the quick-setting procedure according to the invention does not lead to a burden on the watch's motor and, therefore, to an unnecessary expenditure of energy it is also advisable for the indexing pawl, in its rest position, to be free of the toothed rim of the date indication carrier.
One particularly advantageous embodiment is provided with a driving gear designed as a self-blocking, toothed indexing gear for the normal activation of the date ring. Thus no stop spring, or the like, dissipating energy is required to secure the date ring when indexing is not in process since the driving gear takes over this function. This sort of driving gear is often generally designated (strictly speaking incorrectly) Geneva driving gear although this driving gear represents only one special instance of this self-blocking, toothed indexing gear.
The simplest way of achieving disengagement of a gear element, which serves the normal indexing of the date ring, when actuating the quick-setting procedure, is by providing the disengageable gear element with a support elastically yieldable for disengagement. If the position of the date indication carrier is corrected by actuation of the push button mentioned, the gear element, which is disengageable and formed in particular as a pinion, will, if the device is designed accordingly, lift automatically out of the teeth of the next gear element under the effect of the torque exerted by the date ring and jump over one, or if necessary several, teeth where it will be re-engaged at the end of the quick-setting procedure under the influence of the elastic return forces. On the other hand, the elastic return forces for the disengageable gear element are quite easily selectable such that the driving gear can still reliably prevent the date ring from uncontrollably readjusting itself under the influence of the shocks which occur when using the watch.
If the disengageable gear element is held in its engaged position by spring tension it is to be recommended that a stop, which is operative in the direction of engagement, be provided for the movement of the bearing in order to prevent the disengageable gear element being forced against the adjacent gear element by the spring tension--this would impair the easy action of the driving gear and expend energy unnecessarily. Such a stop also permits an increase in the spring tension, which serves to secure the date ring and affects the disengageable gear element, without impairing the easy action of the driving gear.